A solar-driven degradation-evaporation strategy for membrane self-cleaning in the efficient separation of viscous crude oil/ water emulsions

Membrane separation techniques are promising methods for effectively treating hazardous emulsified oily wastewater, but membrane fouling remains a serious challenge because the high viscosity and complex composition of crude oil make it easy to adhere to membranes and difficult to be removed by conventional physical or chemical cleaning means. Herein, a two-stage solar-driven (photo-Fenton degradation/evaporation) strategy was proposed to realize the self-cleaning of membranes fouled by viscous crude oil (>60,000 mPa s), wherein the photo-Fenton process helped to degrade the heavy components into light components, and all light components removed during the solar-driven evaporation process. A 1D/2D heterostructure membrane with photo-Fenton activity and anti-crude-oil-fouling performance was prepared via a facile self-assembly vacuumassist method. The addition of rod-like g-C3N4 (RCN) increased the interlayer distance of alpha-FeOOH/porous gC3N4 (FPCN) nanosheets, resulting in a high permeation flux. The FPCN-RCN membrane exhibited both high permeation flux of 779 +/- 19 L m(-2)h(-1)bar(-1) and a separation efficiency of 99.4% for highly viscous crude oil-inwater emulsion. Importantly, the viscous crude oil fouled on the membrane was completely removed by the photo-Fenton degradation/solar-driven evaporation strategy, and the flux recovery rate of the membrane was similar to 100%. Therefore, the FPCN-RCN membrane combined with the novel self-cleaning strategy exhibits great potential for practical emulsified oily wastewater treatment.

Automated summary

A two-stage solar-driven self-cleaning membrane separation strategy was proposed for effectively treating hazardous emulsified oily wastewater. A 1D/2D heterostructure membrane with photo-Fenton activity and anti-crude-oil-fouling performance was prepared, which exhibited high permeation flux and high separation efficiency for highly viscous crude oil-in-water emulsion.